In a conventional micro-flow rate control valve, it has been a common practice to generate a micron-order displacement by piling up a number of piezo-electric elements. These many piled-up piezo-electric elements are housed in a small space, for example, of 20 mm.times.50 mm.times.50 mm.
However, because the piezo-electric element is expensive in cost, this conventional practice poses economic problems.
It is therefore conceivable to use a lever displacement enlarging mechanism based on a single piezo-electric element (see Japanese Provisional Patent Publication No. H4-218,981).
Conventional cases have however the following problems:
(1) In the design of this displacement enlarging mechanism, components must be housed in a limited space as described above. However, a size capable of being housed in this limited space makes it impossible to achieve a desired ratio of enlargement particularly because of a limited lever ratio. Increasing a size of a lever is naturally conceivable, but an increased lever ratio leads to a larger shape, resulting in a larger-sized apparatus as a whole, and also in a lower transmitting efficiency of the amount of displacement and of the generated force to the output end.
(2) As it is the usual practice to apply a preliminary pressure by directly pressing the piezo-electric elements by means of bolts, the piezo-electric elements may sometimes be broken.
(3) Since the lever of the lever displacement enlarging mechanism is not provided bisymmetrically, a rotating component is added to a displacement. So, the enlarged amount of displacement of the piezo-electric elements cannot be transmitted as it is.
(4) Because the force point, the fulcrum and the action point are not arranged on a straight line, the direction of displacement would contain a rotating component, this resulting in displacement of the output displacement section of the mechanism while curving. It is therefore difficult to keep straight forwarding property, and furthermore transmission efficiency of the amount of displacement and the generating force decreases.
In view of the circumstances described above, the present invention has an object to provide a large displacement enlarging ratio while achieving downsizing of the apparatus.
Another object of the invention is to realize prevention of breakage of an actuator element, and easy adjustment of the preliminary pressure.
A further object of the invention is to ensure straight forwarding property of the output displacement section.